Multiple radius punch for pipe bending



Sept. 16, 1969 L. sums-ram 3,456,919

MULTIPLE RADIUS PUNCH FOR PIPE BENDING Filed Dec. 8, 1967 2 Sheets-Sheet 1 'lillii INVENTOR LOUIS BLEDSTEIN ATTORNEYS P 6, 1969 L. BLEDSTEIN MULTIPLE RADIUS PUNCH FOR PIPE BENDING Filed Dec. 8, 1967 2 Sheets-Sheet 2 INVENTOR LOUIS BLEDSTEIN BY (M,&u1-\d [-{.--l-.2S

ATTORNEYS Fig. 1

United States Patent 3,466,919 MULTIPLE RADIUS PUNCH FOR PIPE BENDING Louis Bledstein, Indianapolis, Ind., assignor to Arvin Industries, Inc., Columbus, Ind., a corporation of Indiana Filed Dec. 8, 1967, Ser. No. 689,076 Int. Cl. B21d 9/05 US. Cl. 72-389 Claims ABSTRACT OF THE DISCLOSURE A machine for forming multiple radius bends in tubing, comprising a press having a ram mounted thereon for reciprocating movement, and having a multiple radius punch attached to the work end of the ram for cooperationwith a pair of dies. The portion of the punch which contacts the tubing is curved convexly with at least two radii of curvature along: its longitudinal axis, and it is -curved concavely across .its transverse axis to correspond to an amount less than half of the circumference of'the tubing. The dies support the tubing horizontally prior to the punching operation, and each die is also curved concavely to correspond to the other half of the tubing circumference. The dies are pivotally mounted and spaced apart sufficiently to allow the punch to move therebetween and to bend the pipe without jammin g it between the punch and the dies.

Background of the invention Punching machines for forming bends in tubing are known in the prior art. The US. Patent No. 3,021,886, to K. D. Ferris, for example, shows a punch having a pair of pivotally mounted dies mounted therebelow for use in forming such bends. Such prior art, however, does not contemplate forming a multiple radius bend in a single operation. Prior to to this invention it was necessary to form such multiple radius bends by means of several punching operations, and it was necessary to leave a straight portion between the tangent points of the bends so that the different punching operations could be performed.

It is an object of this invention to provide a tube bending machine for forming multiple radius bends in a single operation wherein each bend may be immediately adjacent another bend.

Summary of the invention In accordance with my invention I provide a press for forming multiple radius bends in tubing such as, for example, in exhaust pipes for automobiles. The press is provided with a vertically movable ram having a punch attached to its lower end, said punch having its longitudinal dimension curved convexly to conform to the desired curvature which is to be formed in the tubing. The convex curvature of the punch is defined by at least two radii, thereby permitting multiple radius bends to be formed in a single punching operation. To distribute the ram force evenly along the convex surface of the punch, the ram punch connection is centered between vertical lines through the centers of rotation of said radii. The tubing engaging face of the punch is also curved in the transverse direction, but in this case the curvature is concave and forms a semi-circle conforming to one half the circumferential curvature of the tubing which is to be bent.

The tubing is supported on a pair of wing dies, each being pivotally mounted on the press and having a concave curvature to support one half the outer surface of the tubing. Thus, the concavity of the punch and of the dies supports the tubing against cross-sectional deforma- 3,466,919 Patented Sept. 16, 1969 ice tion during the punching operation. The spacing between the pivotal centers of the wing dies is slightly greater than the longitudinal dimension of the punch, so that when the punch is lowered the tubing is not jammed between the punch and the dies.

Brief description of the drawing The accompanying drawings illustrate the invention. In such drawings:

FIG. 1 is a front elevation of a tube bending press embodying my'invention;

FIG. 2 is an enlarged view of a portion of FIG. 1, showing the punch in a raised position over a straight piece of tubing which is to be formed with a bend;

FIG. 3 is a view similar to FIG. 2 but with the punch in a lowered position; and

FIG. 4 is a sectional view taken along lines 4-4 of FIG. 2.

Detailed description of the invention As shown in FIG. 1, a press 10 is provided for forming bends in a length of tubing 12 disposed between a punch 14 and pair of wing dies 16 and 17. In the illustrated embodiment, the punch 14 is mounted on the bottom end of a ram 18 which is actuated by the press to move upward or downward. The dies 16 and 17 are mounted on pivotal wings 20, each wing having a shaft 22 fixed thereto and supported in bearings (not shown) on the press. The longitudinal configuration of each wing is such that each die assembly, or wing die combination, has its center of gravity vertically aligned with its center of pivotal movement. Thus, the dies 16 and 17 are always disposed in a horizontal plane when the ram is in a raised position. The dies are free to pivot, however, when the punch 14 engages the tubing 12 and forces it in a downward direction.

As shown in FIGS. 2 and 3, the punch 14 forms bends in conformance with its curvature along its longitudinal dimension LL. Said curvature is convex and is defined by the arcs of two radii centered at r and r respectively, thereby permitting multiple radius bends to be formed in a single punching operation. The adjacent transverse faces of the punch 14 and the dies 16 and 17 are curved concavely and oppose each other to conform with the circumference of the tubing 12. The concavity is uniform and has a uniform depth in both the punch and the dies. Dies 16 and 17 lie in a straight line, their inner ends being closely adjacent each other and directly under the portion of the punch which forms the deepest point in the bend. Therefore, the tubing 12 is supported circumferentially at each point along its length where bending forces are applied, and cross-sectional deformation of the tubing is substantially prevented. The spacing between the pivotal centers of the wings 20 is greater than the longitudinal length LL of the punch, such that the ram 18 will not become jammed when it forces the punch 14 to a position where its upper surface is even with or below the pivotal centers of the wing dies.

In the embodiment shown in the drawings, the punch 14 has two curvatures and the point of deepest penetration of the punch does not fall at the tangent A between the two curvatures. Thus, the center points of the radii r, and r do not lie on a common vertical line, but rather, are separated horizontally. The ram is longitudinally centered between r and r to provide the most efiicient distribution of force on the tubing 12.

For ease of manufacture, the punch 14, as shown in FIG. 4, is desirably formed in two longitudinal sections 24 and 25 having equal thicknesses, each section providing one half the transverse concave curvature of the punch. The sections 24 and 25 are placed together and joined with a plurality of bolts 26 which pass through holes 28 in section 24 and are threadably held in section 25. The upper-face of the punch 14 is provided with a series of threaded holes for reception of bolts 30 which secure the ram 18 to the punch 14. The bolts pass through holes 32 in a flange 34- formed on the lower portion of the ram.

I claim:

1. An improved tube bending machine for forming multiple radius bends in a single operation, said machine comprising a reciprocably movable ram, a punch mounted on said ram for movement therewith, said punch having a tube engaging face provided with a longitudinal convex curvature defined by a plurality of arcs having different radii, and a pair of die assemblies pivotally mounted on said machine in alignment with each other and with said punch.

2. A tube bending machine as set forth in claim 1 in which the tube engaging face of the punch is transversely curved with a uniform depth concavity substantially equal to one half the outer circumference of the tube, and

said punch comprises two longitudinal sections joined together, each section providing one half of the concave curvature.

3. A tube bending machine as set forth in claim 1 in which said convex curvature is defined by two radii, and said ram is attached to the punch at the longitudinal center between the center points of the two radii.

4. A tube bending machine as set forth in claim 1 in which the tube engaging faces of said die assemblies are longitudinally aligned and are transversely curved along their lengths with uniform concavities to conform to the outer circumference of the tube, said tube engaging face of the punch is transversely curved along its lengths with a uniform depth concavity along its longitudinal curve to correspond with a portion of the outer circumferential curvature of the tube, and said die assemblies lie closely adjacent each other with their adjacent ends being disposed in alignmnt with the deepest penetration point of the punch when the punch is in a retracted position.

5. A tube bending machine as set forth in claim 1 with the addition that means are provided to maintain the die assemblies in longitudinal alignment when the ram is in a retracted position.

6. A tube bending machine as set forth in claim 1 in which said punch is vertically movable and each die as- 4 sembly has its center of gravity in vertical alignment with its center of pivotal movement to maintain the die assemblies in horizontal alignment when the ram is in a raised position.

7. A tube bendingmachine as set forth in claim 6 in which the pipe engaging faces of the die assemblies are longitudinally straight and transversely curved along their lengths with uniform concavities to conform to the outer circumference of the pipe, said tube engaging face of the punch is transversely curved with a uniform depth concavity along its longitudinal curve to correspond with the outer circumference of the tube, and said die as semblies lie closely adjacent each other with their adjacent ends beingdisposed on a vertical line'with the deepest penetration point of the punch when the punch is in a raised position.

8. A punch for use in combinationwith a tube bending machine, said punch having a longitudinally extending convex curvature along its tube engaging face, said curvature being defined by a plurality of arcs having different radii.

9. A punch as set forth in claim 8 with the addition that said engaging face is transversely curved with a uniform depth concavity to conform with a portion of the outer circumferential curvature of the tube.

10. A punch as set forth in claim 9 in which said punch comprises two longitudinal sections joined together and ,each section forms one half of said concave curvature.

References Cited UNITED STATES PATENTS 791,193 5/1905 Heer 72-389 2,451,302 10/1948 Peters 72389 3,021,886 2/ 1962 Ferris 72-389 3,196,661 7/1965 Lance 72-389 3,339,385 9/1967 Lance 72-389 CHARLES W. LANHAM, Primary Examiner G. P. CROSBY, Assistant Examiner US. Cl. X.R. 72-394 

